The present invention relates to a modular transport system for opening and closing Venetian blinds, pleated shades, and other blinds and shades. While the embodiments shown herein are of horizontal blinds, the transport system may also be used on vertical blinds.
In order to proceed, it is necessary to explain the operation of a blind transport system and to define some of the terms used. Typically, a blind transport system will have a top head rail which both supports the blind and hides the mechanisms used to raise and lower or open and close the blind. The raising and lowering is done by a lift cord attached to the bottom rail (or bottom slat). Thus, when raising a blind, at first only the bottom rail is being raised and the amount of force required is small. As the bottom rail is raised further, more of the slats are stacked on top of the bottom rail and thus progressively more force is required to continue to raise the blind. The largest amount of force will be required at the very top when literally the entire blind is being raised. By the same token, the greatest amount of force will be required to keep the blinds in this fully raised position, as one is fighting against the weight of the entire blind.
In contrast, when the blind is fully lowered, only the bottom rail is supported by the lift cord. The rest of the weight of the blind is supported by the ladder tape which has tilt cables running to, and supported by, the head rail. Since the weight of all slats not resting on the bottom rail is supported by the head rail (via the ladder tapes), this weight need not be overcome when raising the blind. Only the weight of the bottom rail, and the weight of each successive slat as it comes in contact with the bottom rail as the blind is raised, need to be overcome.
In essence, the lift cord and the ladder tapes exchange loads as the blind is raised and lowered. The ladder tapes do practically all of the supporting when the blind is down. As the blind is raised, the weight is shifted from the ladder tapes onto the lift cords as each successive slat is picked up by the rising bottom rail and thus is no longer supported by the ladder tapes. The implication is that the least amount of force is required to start raising a fully lowered blind, and also the least amount of force is required to keep the blind in this lowered position. Progressively larger force is required to lift and to maintain the position of the blind as the blind is raised until a maximum amount of force is reached at the topmost position, where the blind is fully raised.
The force required to raise the blind varies directly and approximately linearly with the raising of the blind, increasing from a minimum when the blind is fully lowered to a maximum when the blind is fully raised. This same force also varies directly and approximately linearly with the size and weight of the window covering.
The basic concept for a blind transport system is described in U.S. Pat. No. 13,251, xe2x80x9cBixlerxe2x80x9d, issued Jul. 17, 1855, which is hereby incorporated by reference. However, the coiled spring motor used by Bixler is not a constant force motor. As the blind is pulled down, the spring is coiled tighter. Thus, the spring provides the strongest force when the blind is down, which is when the least force is required to assist in lifting the blind.
Other relevant blind transport systems provide a spring that gets stronger as the blind is lowered and weaker as the blind is raised, exactly the opposite of the desired effect. These systems may use a ratchet mechanism or brake to compensate for this shortcoming.
As the blind is lowered, its weight and the force of gravity are used to wind up the spring so that the unwinding of the spring may assist in the raising of the blind. In order to accomplish this raising of the blind, there is generally some type of mechanism to wind up the lift cord onto a shaft or spool. Preferably this mechanism will pull the lift cord vertically, with no horizontal component to upset the symmetry and functionality of the ladder tapes.
Many lift cord winding mechanisms have been used in the prior art. Typically they displace the wind-up spool axially as the lift cord is wound up, requiring a. complicated mechanism, or they have problems with over wrapping and tangling of the cord. In order to prevent this over wrapping or tangling, some mechanisms guide the incoming coils of the lift cord axially along the spool using either a shoulder on the spool or a finger or kicker in close proximity to the surface of the spool. In the prior art, the kicker is located at the bottom of the spool, just before the point where the new lift cord enters. The weight of the blind pulls the spool downwardly, causing it to sag, and this can cause the gap between the kicker and the spool to be reduced to the point that there is interference between the spool and the kicker, creating friction.
As may be appreciated from the prior art, the purpose of the spring motors is primarily to assist in raising the blind. Thus, a mechanism must be found to transfer and control the force from the spring motor to the lift cords, and to do so such that all the cords are lifted the same amount simultaneously (so the blind is raised evenly), and such that the cords are pulled only vertically with no horizontal component.
A complete blind transport system must also include mechanisms to accomplish other tasks. Primary among these other tasks is the ability to open or close the blind via tilting of the individual slats. This is typically accomplished with ladder tapes (and/or tilt cables) which run along the front and back of the stack of blinds. The lift cords, in contrast to the tilt cables) typically run through slits in the middle of the slats and are only connected to the bottom rail.
When the blind is closed on a standard window shade, the slits through which the lift cords run become quite visible and allow light to pass through the blinds. It is desirable, for aesthetic reasons, to have a window covering product where there are no slits visible such that, when the blind is closed, there is no light passing through the blind. This is referred to as a xe2x80x9cde-lightedxe2x80x9d product and is a desirable product or feature.
The prior art shows that blind transport systems have traditionally been custom-designed and custom-built around the needs of a particular window covering. Each element in the transport system must be carefully fabricated and modified as required for it to meets its function as well as its physical placement within the system. All the different elements must be carefully mounted and placed so they will co-operate with each other and this is done at the expense of much time. Furthermore, changing even one single characteristic of the blind (such as going from lightweight vinyl to heavy wooden blinds, or simply increasing the width or the length of the window covering) necessitates going through the entire time consuming process of customizing the entire blind transport system. The nature of this process makes it expensive to truly customize a system in order to optimize its performance.
The primary objective of the present invention is to provide a modular blind transport system which overcomes the shortcomings of prior blind transport systems. Rather than having to design a completely new system for each size and weight of blind, the designs of the present invention provide a system comprised of individual modules which are readily interconnected to satisfy the requirements of a multitude of different blind systems, it also includes the individual modules which make the overall system possible.
Accordingly, modularity is an important feature of the present invention. The individual modules in the present invention are contained in housings which make each element an independent and self contained module. Each module is easily and readily installed, mounted, replaced, removed, and interconnected within the blind transport system with an absolute minimum of time and expense. Each housing provides the mounting mechanism for its module onto the blind transport system, and removal of the housing also removes all the individual components which make up the module, leaving the balance of the blind transport system essentially unaffected except perhaps for the need to use a longer or shorter connecting rod.
Likewise, interchangeability is another important feature of the present invention. Individual modules may be removed and replaced with other modules which fit in the same location and have the same method of interconnection and installation, but which have different performance characteristics. For instance, interchangeable transmission modules may have different transmission ratios, or may even be a different type of transmission than the ones disclosed in this specification such a gear-type transmission, or interchangeable power modules may have different strength coil springs or may even be other types of power modules such as low voltage electric motors or a manually driven cord drive.
The present invention overcomes the problem of the high friction and the interference fit between the wind-up spool and the kicker which acts as a shoulder to displace the coils of the lift cord such that there is no over-wrap. This is accomplished by moving the location of the kicker such that it no longer is immediately below the wind-up spool but rather is located beside the wind-up spool. Thus, any vertical displacement of the wind-up spool due to the weight of the blind will not adversely affect the clearance between the spool and the kicker.
A blind transport system in accordance with the present invention may have four functional groups, and each group may have a number of different modules to accomplish its function in different manners. The four groups are:
1xe2x80x94Power and power transmission group: may include a head rail, a lift rod, a tilt rod, a coaxial motor, a transaxial motor, a low power electrical motor, a ratchet-type drive mechanism, variable force coil spring motors, a worm gear lift mechanism, a cord loop lift mechanism, a variable brake, an adjustable brake, a transmission, and the adapters to interconnect these modules. More than one of any of these modules may be present
and any one or more of these modules may be absent in a power transmission group for a particular blind.
2xe2x80x94Lift and/or tilt stations group
3xe2x80x94Tilt mechanisms group, which to a large extent is a specific subgroup of the power and power transmission group, but geared specifically at the tilting action of the blind.
4xe2x80x94The rest of the blind, which is essentially anything hanging off of the head rail including slats, ladder tapes, bottom rail, handles, pleated fabrics, handles, etc.
It is important to note that a particular blind transport system may include more than one of any of these groups, and it may also be that any one or more of these groups are absent in a particular blind transport system. For example, a pleated fabric shade system would have no need for a tilt mechanism.
Most blinds made in accordance with the present invention include a head rail and a power transmission rod. This does not mean that the head rail and the power transmission rod are always identical. For instance, the power transmission rod may be longer or shorter depending on the application, and the head rail may also be longer or shorter or it may be wider or narrower also depending on the application. However, the head rail is not always necessary, and in some cases the lift spool itself serves as the power transmission rod. Also, specific modules of this invention may be used in other applications without the presence of the head rail or of the power transmission rod.
By properly sizing and designing the individual modules, they can be made to work together interchangeably, permitting the development of a wide range of systems with a minimum number of different parts. For instance, a window covering may call for a certain size lightweight plastic blind including one coaxial coil spring motor, one transmission, and two lift stations. The same type of window covering but out of a much heavier wooden blind and for a much wider window may require two or more of the same coaxial coil springs motors connected in series, a similar transmission but with a different range, and several lift stations.
By using a modular concept at the system level, a relatively small number of modules can be arranged to achieve a very much larger number of combinations for an extremely wide range of applications. Furthermore, the modular concept is incorporated not only at the system level with the design and use of modular components; it is also carried out at the module level such that individual modules share parts, in as much as possible, with other modules. Thus, for example, the same housing for a coaxial motor may be used for a number of different coil springs, or the same housing for a transmission may be used with different configurations of input and output shafts to achieve different transmission ranges. Thus, again, a relatively small number of parts can be arranged to achieve a very much larger number of modules for an extremely wide range of applications.
The xe2x80x9cde-lightedxe2x80x9d product discussed earlier may be accomplished in the present invention by one of two possibilities:
1xe2x80x94The lift cords pass through every slat but not through a slit in the center of each slat (as in the standard rout design), but through a smaller slit offset, preferably toward the back of each slat, such that when the blind is closed, the overlap of each slat totally covers this slit on the adjacent slat. This works well especially for short blinds, lightweight blinds, and narrow blinds.
2xe2x80x94Instead of having a single lift cord at each lift station passing through a slit (or rout hole) in the center of each slat, there are no slits in the slats and there are preferably but not necessarily two lift cords at every lift station, one in front and the other in rear of the slat (the same as the ladder tapes for tilting the slats). As is the case with lift cords for standard rout products, the lift cords for de-lighted products are not attached to any of the slats, only to the bottom rail.
In some embodiments of the present invention, the coiled spring motor power unit provides sufficient force, in combination with the system inertia, to balance the weight of the blind so that, when a user touches the blind and urges it up or down, the blind easily moves in the direction it is urged and will then stop when the user stops urging it and will remain in that position. The spring motor preferably is a constant force motor, but the force required to balance the blind varies as the blind is moved up and down, with the greatest force required in the raised position and the least force required in the lowered position. This is especially the case for the type of window covering product that bundles up as it is raised to the head rail such as a Venetian blind (as opposed to one that rolls up, such as a roller blind, which in fact exhibits an opposite relationship of force required relative to blind position but which may also use the components of the present invention). For that reason, it is usually desirable to use a transmission, so that the proper amount of force is provided at all positions of the blind.
The modular blind transport system, including any of the first three groups (power and power transmission, lift and/or tilt stations, and the tilt mechanisms), is intended to work as a unit, often within the confines of a rail. This rail may be a head rail, a bottom rail, a moving rail, or an intermediate rail. For the purposes of this application only, we will use the term head rail with the understanding that we mean any of the aforementioned rails.
For heavier blinds, it can become difficult to fit all the components within the head rail, particularly the coil spring motor modules. Some solutions to that problem are presented here. One solution is to use one or more transaxial motors instead of a coaxial motor. Another solution is that a transmission cord has been discovered which can be made with a very small diameter and yet be strong enough to carry the load, which permits the shafts of the transmission to be short enough and strong enough to handle the job while still fitting in the head rail.
In an effort to logically and methodically cover the material of this invention, a typical first preferred embodiment of a complete modular blind transport system in accordance with this invention will be described in detail. Then, variations in particular modules will be described. Finally, having described these variations in particular modules, alternate preferred embodiments of complete blind transport systems using the various modules will be described.